BiologicalJoumalofthe LinneanSociely, 12:327-348. With I I figures
December 19 79
The relationships of plant and insect diversities
in succession
T. R. E. SOUTHWOOD, V. K. BROWN AND P. M. READER
Department ofZoology and Applied Entomology, Imperial College, London
Accrpledjor puhlicalion April 1979
The basic feaures of an intensive study on the various stages o f a secondary succession, from fallow
lield to birch woodland, are described. The a+ diversities of the green plants, and two orders of
insects, Heteroptera and adult Coleoptera, are described. For the vegetation, in addition to
taxonoinic diversity, structural diversity, with both spatial and architectural components, was
recognized. I t was found that up to a successional age of 16 months, the taxonomic diversities of
plants and insects rose; therealter the diversity o l t h e plant species declined far more than the insect
species diversity. I t was concluded that in the later successional stages the maintenance o f a high level
01’ taxonomic diversity of these orders of insects is correlated with the rising structural diversity of
the green plants, which virtually compensates for their falling taxonomic diversity. The larger fungi
appear t o sliow a similar trend to the insects.
KEY WORDS: - succession - taxonomic diversity - structural diversity - green plants - Colroptera Heteroptera
CONTENTS
. . . . . . . . . . . . . . . . .
Introduction
The expression of diversity
. . . . . . . . . . .
Tlie sites
. . . . . . . . . . . . . . . . .
Methods
. . . . . . . . . . . . . . . . . .
Sampling
. . . . . . . . . . . . . . . . .
Recording and analysis
. . . . . . . . . . . .
Kesults and discussion . . . . . . . . . . . . . . .
Taxonolnic diversity of the vegetation
. . . . . . . .
Structural diversity o f t h e vegetation
. . . . . . . .
Taxonomic-diversityofthe Heteroptera and Coleoptera . . .
Coinparison of plant and insect diversities
. . . . . .
Suniniary and conclusions
. . . . . . . . . . . .
Arkriowledgeinents
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Keterences
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INTRODUCTI 0 N
“Many structural and functional attributes of the community change during
its successional development” (Ricklefs, 1973). Indeed one of us has suggested
that succession provides one of the cardinal axes of the habitat templet within
which the ecological strategies of community components (plants and animals)
may be organized (Southwood, 1977a). Succession may be viewed as a process
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0 1979 The Linnean Society of London
328
T. R.E. SOUTHWOOD E T A L
that follows a disturbance or disaster (Harper, 1977);its characteristic feature is
that, as the patch of habitat in question moves through the successional processes
there is an increase in durational stability, the length of time it remains in a
particular condition (humus level, dominant plant, etc.). Thus the favourableness of habitats that are early in the successional sequence will vary greatly in
space; highly favourable habitats will arise in new locations, a feature termed by
Baker ( 1978)the “ontogeny ofhabitat development”.
However, in spite of Ricklefs (1973)general statement, quoted above, he goes
on to state (correctly we believe) that “the complexity of community organization
along a successional gradient has never been measured”. I t seems that although
various components have often been assessed over a portion of a successional
gradient, a holistic study has not been made. Such a study is necessary to test the
predictions that arise from many, often firmly established, generalizations with
regard to properties such as productivity, diversity, trophic links or concepts,
such as apparency (Feeny, 1976; Southwood, 1977b) and r and K selection
(MacArthur, 1960; Pianka, 1970)and their relation to succession.
The present paper is the first of a series that will describe an intensive study on
the characters and attributes of the macro-organisms of a typical secondary
succession in southern Britain. It relates the taxonomic diversity of two groups of
insects, Coleoptera and Heteroptera, to the taxonomic and structural diversity of
plants in a succession.
The expression ofdiversity
A general association between plant and animal diversity has long been
recognized. However, a number of different properties contribute to diversity.
That most usually considered is the number of different species and its relation to
number of individuals, we refer to this as taxonomic diversity. However,
structure is also important; the relevance of plant structure to the diversity of
birds has often been demonstrated (MacArthur & MacArthur, 1961; Karr, 1968;
Recher, 1969; James, 1971) whilst Lawton (1978) has recently stressed the
probable role of plant architecture in relation to insect diversity. The shape or
form of an animal is a comparable character (Van Valen, 1965; Findley, 1973).
We believe that for vegetation it is useful to distinguish two components of
structural diversity: spatial diversity, the distribution of plant structures in space
above ground level and architectural diversity, the distribution of different types
of plant structure (Table 1).
An important study on the relationships of insect and plant diversities is that of
Murdoch, Evans & Peterson (1972) who investigated these in three “Old Field”
sites, using leafhoppers (Homoptera : Auchenorrhyncha). They confirmed the
general correlation between plant and animal diversity, but because the
structural (spatial) and taxonomic diversity of their lants were in all cases
positively correlated, they were unable to resolve the inf;uence of these variables
on the taxonomic diversity of the insects.
The sites
The Imperial College Field Station at Silwood Park, Ascot, Berkshire, consists
of 93 ha (230 acres) and is a mosaic of vegetational types, principally arable
PLANT AND INSECT DIVERSITIES
Table 1 . Plant architecture-types
Dcatl wood o v e r 10 cin dia.
Drad wood over 2 crn dia., under 10 em
Dt-ad w o o d under 2 cin dia.
Bark on dcad wood over 10 ctn dia.
Bark on cleat1 wood 2-10 cni dia.
Bark o n dead wood under 2 cin dia.
Bark on living wood over 10 crn dia.
Bark on living wood 2-10 crn dia.
Bark o n living wood under 2 cm dia.
Grrcn Slellls
Leavrs ot non no cotyledons
Petioles
Leal surlace-upper
(if.distinct)
Leal surfhce-lower
Leal buds/rcales
Flowering S ~ C ' I I I S
329
of structure
F l o w c ~buds
01>rnliowers
Drad Ilowcrs inm covered by next item-e.g.
Riprning/ripr h i t s (seeds)
Old ltuitiiig structures
Dead lcaves
old ratkins)
Dead Stellls
Mosses-epip h ytes
Mosses-on soil surlace
Livrtworts-epiphytes
Livrrworts-on soil surfice
Lichens & algae-epiphytes
Liclirns & algac-on soil surface
Fungal truiting bodies--on vegetation
b'uiigal tiuiting bodies-on soil surface
crops, grassland and woodland. Our study sites, selected to represent various
ages in the secondary succession, were typical of types represented in several
localities in Silwood Park and were within 250m of each other. We therefore
consider that there is no great spatial barrier to colonization of any of these sites
by the same organisms. Each site is on slightly raised ground, of area 405 m2, and
is part of a larger region of similar vegetation. In 1977 all three sites were fenced
with wire-netting to exclude rabbits, this was only partly successful, so that each
site continued to be lightly grazed by young rabbits. The three sites were:
Youngfield
This site is part of a long-standing arable area; it was treated with weed-killer
to destroy perennial weeds, shallow ploughed, harrowed and lightly rolled in
mid-March. This field was six weeks old at the time of the first sample. The young
field, so prepared in 1977, was left undisturbed in 1978 providing information
for the second year of a secondary succession. A new young field was established
in March 1978 in a similar situation.
Oldfield
In 197 1 the soil excavated for the construction of a substantial building (the
'Nuclear Reactor Centre') was covered with top soil (from the site) and left
undisturbed apart from fairly severe rabbit grazing in 1975-6. This was thus a six
year old site in 19 7 7 , at the start of the project.
Woodland
This site was a small section of a large birch-dominated woodland with an
occasional large oak (Quercus robur) and beech (Fagus syluaticu). Typically for the
acid gravels, on which the sites occur, birch (Betulu pendula and B. pubescens)
dominated the secondary growth, after selective felling in 1947.
The equivalent successional age of this site is uncertain, for it was woodland
prior to 1947 when Imperial College acquired Silwood Park. However, there are
other sites at Silwood where a similar vegetation has developed but, on which the
birch trees are much older. These were regularly grazed by cattle until the First
World War, thereafter grazing was discontinued and the trees developed
naturally. Thus we consider that the age of our woodland site is around 60 years.
330
T. R. E. SOUTHWOOD E T A L .
However, birch may not be the climax to the sere (Tansley 1939). We recognized
that the low taxonomic diversity of the vegetation of this late successional stage,
would allow for the separate consideration of the different aspects of diversity.
METHODS
Sampling
Sampling plan
A stratified sampling programme was followed in order to reduce systematic
errors and to speed and simplify the sampling process. Each site was divided into
45 squares, 3 x 3 in, arranged in a 9 x 5 pattern. The actual samples were then
taken within these squares as described below. In the Woodland site a scaffold
and board ‘cat walk’, 7 m long, was erected diagonally across the plot; the
platform level was at 6 m. Five complete samples were taken throughout the year
at times that were judged to reflect biological seasons, namely: January, early
May, early June, early July and mid/late September. Additional vegetational
samples were taken in late July and late August in 19 7 7 .
Vegetation
Sampling pins were the principal method used; they were marked at intervals
of 25, 2 5 , 50 and successive 100’s mm from soil level. Generally a 550 mm long
pin was adequate, but in tall vegetation a 1 m pin was required. In the woodland
site a 10 m pole of bamboo rods was used, it was divided into ten sections and
held on a 1 in high stake (i.e. it sampled up to 1 1 m). Additionally in the
woodland site, a helium-filled weather balloon buoyed on string marked in
metres was used and the 1 m sampling pin was placed through the vegetation
around the ‘tree-top cat walk’. The total number of samples taken is shown in
Tables 2 and 3, usually five samples were taken from each square by throwing the
sampling pin haphazardly, from each corner and centrally. In the woodland site
ground cover was sampled in this manner. For the trees the tall pole was placed
within each square in a position determined by throwing a sampling pin. The
data from the balloon and ‘cat walk’ methods were used to correct the pole
surveys; the former with regard to vegetation over 11 m above ground level and
the latter for the details of plant architecture in the canopy. Inevitably these
estimates for the tree canopy were less accurate than those for the field layer, but
the mean number of touches in 1978, namely 16.5, compared reasonably with
the 17.5 estimated in 1977. We are not concerned with percentage cover, but as
the sampling pins were 4 mm in diameter the number of touches would slightly
overestimate this feature.
Fruiting bodies of the larger fungi were sampled by counting those present in
nine randomly selected squares in each site in October 1977.
M acro-invertebrates
On field layer vegetation these were sampled with a D-vac suction apparatus.
One sample was taken from approximately the centre of each 3 x 3 m square: to
simplify sorting and other procedures five samples (i.e. from one line of squares)
were combined in the field (taken successively without emptying the bag). Thus
there were nine main samples from each site on each occasion, each of five
PLANT AND INSECT DIVERSITIES
33 I
subsamples, and representing the fauna from 0.47 m2. The D-vac apparatus was
held in position for 1 min, after it was removed the spot was carefully searched by
eye and any invertebrates still present collected : Mollusca, Isopoda and large
Coleoptera were amongst those commonly found. In the Woodland the leaf litter
was covered with a piece of 35 mm mesh wire-netting. This restricted the number
of fallen leaves entering the suction apparatus and prevented clogging of the bag.
The bracken, when fully grown, was sampled separately. The arboreal fauna was
sampled with a specially designed beating bag; it was found that the bag
prevented the escape of the active insects more effectively than the traditional
tray. Ten ‘bagfulls’ were sampled from the lower canopy, one of these from the
oak tree, that constituted about 10% of the canopy, and ten from the upper (i.e.
from the ‘tree-top cat walk’) on each sampling occasion. This method was
calibrated in relation to the ground surface area i.e. to the D-vac samples by two
approaches: (i) visual estimates by four different persons of the number of
bagfulls per area of canopy, (ii) ‘knockdown’ sampling with a Hudson ULV-BakPak mistblower and 1% pyrethrin insecticide of an area (16 mP)of comparable
canopy near the study site. The visual estimates gave a mean 4.17 bagfulls/mz, the
knockdown based on Heteroptera an estimate of 4.55 bagfulls/mz; thus it was
concluded that 20 ‘bagfulls’ were more or less equivalent to 45 D-vac samples
(i.e. 4.2 m2).
There are 55 living tree trunks on the site and the fauna of these was sampled
by collecting visually with a pooter from ground level to 2 m on five trunks, i.e.
equivalent to 10 m of trunk. Allowing for an efficiency of about 75%and 15 m of
trunk and ,najor branches (too large for the bag samples) we consider that these
catches represented about 1% of the superficial bark fauna on the site. They were
therefore added to the beating and D-vac samples to give an estimate of the total
macro-invertebrates from a column of vegetation in the woodland arising from
4.2 m2 of ground surface (i.e. about 1% of the site). Soil samples were taken from
each site and extracted in Berlese-Tullgren funnels and the avifauna recorded
during simultaneous observations: data from these methods are not used in this
paper so further discussion is omitted.
Recording and analysis
Taxonomic diversity
A measure of taxonomic diversity of the vegetation, comparable to that
normally used for a fauna, was obtained by regarding one or more touches of a
sampling pin by a species as an “individual”. The total individuals for that plant
species was thus the number of sampling pins it touched. The concept of the
individual, used in this way, is inappropriate for trees that may constitute the
canopy over a large area, but it can be used as a measure of the taxonomic
diversity in some hundreds of vertical columns of vegetation, each of diameter
4 mm. The insect taxonomic diversity was assessed in the usual way by identifying
all individuals in a sample to species.
Spatial diversity
The number of touches by a piece of vegetation (any species or any part) was
recorded within each height division of the sampling pins (or poles, these
332
T. R. E. SOUTHWOOD E T A L
corrected for their greater diameter). These data therefore show how plant
structures are distributed vertically in space, the height divisions may be regarded
as categories (analogous to species in taxonomic diversity) and the structures to
individuals. A similar approach was adopted by Murdoch et al. (1972); they
referred to it as foliage height diversity, however, we concerned ourselves with
parts of the plant other than foliage.
Architectural complexity
Lawton (1978) states “there are more ways of making a living on a bush than
on a bluebell” and growth form of the vegetation is indeed likely to be an
influence o n the richness of the associated fauna (Strong & Levin, 1979). We
therefore sought to record the diversity of types of plant structures: the different
categories into which plant structures were separated according to their
architecture are listed in Table 1 . As will be seen these were defined largely on
botanical grounds but cognisance was taken of the way different animals will
utilize plant parts, e.g. on a leaf of a dicotyledon the upper and lower surfaces
provide different habitats, as do living and dead wood, the space between the
bark and the wood is another ‘microhabitat’ only found on dead wood. In
animals form is an analogous variable; studies have been made on vertebrates
4e.g. Karr &James, 19741, but not on invertebrates. A morphometric analysis of
the form in some of the insect groups found in this survey has been undertaken
by one of us and will be reported elsewhere (Brown, in preparation).
RESULTS A N D DISCUSSION
Taxonomic diversity of the vegetation
,ddiversity gradient
Changes in diversity with time occur in all three sites; in the Old Field and
Woodland sites these changes are mostly seasonal for there has been little change
in @-diversityduring the first two seasons. This is evidenced by the high value of
the Ssrensens Index of Similarity (Is= ZJ/A+ B, where J = species present in both
samples; A and B=species present in samples A and B respectively (Table 2)). In
the Young Field the seasonal changes are confounded and essentially dominated
by the changes in basic species composition: the extent to which the Young Field
moves very quickly along a /?-diversity gradient is shown by the relatively low
(0.64)Index of Similarity between the first and second years in the same site. The
taxonomic composition of the Young Field in its second year is only marginally
closer to that in its first year, than it is to the Old Field (Is=0.64cf. Is=0.53). That
this is a successional change along a /&diversity gradient and not simply a
seasonal effect is shown by the higher value of the index (0.74) between the two
Young Fields in their first season, although they represent different sites and
dif‘ferent seasons.
Further evidence of the change in composition of the Young Field over the first
18 months of succession is provided by the species gain (colonization) and loss
(extinction) curves (Fig. 1 ) . I t must be noted that whilst actual colonization will
occur before the species is recorded in the samples, actual extinction is likely to
occur ajer the species is last recorded; therefore the time gap indicated in Fig. 1 is
an underestimate. The rapid accumulation of species in the first season occurred
PLANT AND INSECT DIVERSITIES
333
Table 2. Indices of Similarity (Is) between the flora (green plants) recorded in the
different sites between May and October in two seasons
Total
sanipling
points
2970
2250
2900
2675
2075
3 105
2300
Comparison
Woodland 1977 v Woodland 1978 (same site)
Old Field 1977 v Old Field 1978 (same site)
Young Field 1977 v New Young Field 1978 (same age, different site)
Young Field 1977 v Young Field 1978 (same site, ditterent age)
Young Field 1978 v Old Field 1978 (different ageand sites)
Young Field 1977 v Old Field 1977 (difFerent age and sites)
New Young Field 1978 v Old Field 1978 (different age and sites)
Index
0.87
0.87
0.74
0.64
0.53
0.4.5
0.28
Tme(months)
bigule 1 . Plant species gain and loss rates in Young Field vegetation over two years. 0 , Colonization;
0, rxtinction.
in two main ‘waves’, those that appeared before the fourth month and flowered
during the first season and those that grew in the late summer and autumn.
Undoubtedly the dry spell in the middle of the summer of 197 7 accentuated this,
but even so the 11 species of ‘primary colonizers’ do seem to constitute a
community of ‘ruderals’: of the seven dicotyledons in this group, six were
‘extinct’ (so far as sampling was concerned) within 18 months, though at one
time they were all very abundant. In the new Young Field in 1978 the same
334
T. R. E. SOUTHWOOD ET AL.
seven'' species were recorded after six weeks, along with one further species,
Tripleurospermum inodorum that was not recorded until the twelfth week of 1971.
The /I-diversity relationships of the different sites in the various parts of the
growing season are shown by the Indices of Similarity displayed in the Trellis
diagram (Appendix l ) , these are most easily appreciated by reference to the
dendrogram (Fig. 2) which shows :Young Field
-Old Field
Woodland
77 77 77 ?a 7a i
77 70 77 77 70 70 77 70 TI 77 70 7 0
Jul. S Ma; Jul. S .M Jul Jul SeD Seo M May Jul Sep. Jul. Sep.May
M
I
I
0.90
0.60
T'
0.30
Figure 2. Dendrograin of taxonomic similarity ofvegetation in three sites over two years
(i) The close similarity between the samples from the Woodland site at three
times in each of two years (in May 1978 the bracken (Pteridium aquilinum)
croziers had not risen above the leaf litter).
(ii) The similarity, but not at quite such a high level, between the Old Fiel&
samples.
(iii) The relatively low similarity between the six Young Field samples in the
two seasons. Two groups of samples can be recognized, those two from
the first three months of the succession and the remainder. This supports
the view, derived from Fig. 1 and associated data, that there are really two
communities: ruderals and early successionals in the Young Field.
Thus we can conclude that whereas /I-diversity changes in the Woodland and
Old Field sites are insignificant (over two years) and reflect seasonal changes,
those in the Young Field are a reflection of an underlying change in the structure
CapJella bursa-patons, C h o p o d w m album, Polygonum autculare, Seneno vulgam, Spergulana medta, Stellana media
and Verontcapentca.
j'
PLANT A N D INSECT DIVERSITIES
335
of the community of green plants. Very approximately one can recognize four
<‘communities” : the ruderals, the early successionals (both in Young Field), the
mid-successionals (Old Field) and the late successionals (Woodland). The
distances these are apart on a p-diversity gradient may be estimated by
calculating 1 - Is for each comparison. These are shown in the upper part of Fig.
3, the Is values are those for the whole season, i.e. for a cluster of points and not
for each sampling occasion (as cited in Appendix 1 ) .
a-diversity
This describes the segregation of units into categories, here of records of
individuals into species. There are a number of indices, one of the most useful is
Williams’ a,although the Berger-Parker dominance index (d) is both useful and
simple to calculate (May, 1976; Taylor, Kempton 8c Woiwood, 1976; Southwood,
1978). I n this study, Williams’ a has been employed and was calculated by a
maximum likelihood method. Indices for the vegetation samples are given in
Appendix 2.
It will be observed that the taxonomic diversity of the green plants varies with
the successional age of the site at the date of sampling; if a is plotted against age
in months on a logarithmic scale then a slightly skewed normal curve is described
(Fig. 3, bottom). I t is interesting that thep-diversity distances between the groups
of samples seem to correspond proportionally to the successional age differences
on a logarithmic scale (Fig. 3, top). This suggests that in this sere the species
turnover rate is linear with regard to time expressed as log successional age.
The a-diversity of a sample is well expressed by the dominance diversity
curves; the steeper the slope the less equitable the distribution of individuals
between species. When such plots are examined for different samples (Fig. 4)it is
seen that as diversity rises so the equitability increases; likewise once diversity
falls (after the age of about 16 months in these spring initiated secondary
successions) then equitability falls; there is thus one set of ‘rising’ curves
representing the ruderal and early successional stages and another set of ‘falling’
curves from early to late successional stages (Fig. 4).These changes in form with
age, from an apparently geometric series to an approach towards MacArthur’s
broken-stick model and then back again, have implications regarding the
underlying processes: we intend to explore these in a later paper.
The taxonomic diversity of the green plants (mosses, ferns and flowering
plants) therefore rises and then falls through succession. The diversity of the
fungi, as represented by their fruiting bodies, continues to rise (Appendix 2).
Structural diversity ofthe vegetation
As indicated above this has two components, spatial and architectural and
these have been separated.
Spatial diversity
This is a measure of the distribution of plant structures (of any type or species)
in the vertical plane. Profiles for the three sites show how the level of maximal
density is at ground level in the ruderals; in the mid-successionals stratification is
beginning, whilst in the late successionals the canopy is well formed (Fig. 5 ) . The
woodland canopy is clearly multilayered (Horn, 1971). Lawton (1978, fig. 7.10)
'r.R. E. SOUTHWOOD E T AL.
336
p diversity
0.38
040
0
0
Ruderols
Eorly success1ono1s
A
0 91
n
Mid successionols
Lote successionols
0 .
12
1
1010
42Seed Bonk
01
Young Field
I
Woodlond
Old Field
I
I
1
I
I
Time(months) log N t 1
Figure 3. Taxonomic diversity of the green plants in the study areas. (Top)The distances between the
difliwnt groups 0 1 samples in terms of P-diversity (values for I - I S ) , (Bottom) The a-diversity (as
William' a)for sites plotted against log successional age. 0,Seed Bank; 0,Young Field: 0, Young
Field alter-one year; A, Old Field; A, Woodland.
has postulated how structural diversity will change with season; our data (Fig. 6 )
tend to support his suggestions with maximal diversity in mid-summer ; however,
with woody branches and trunks the spatial diversity of the woodland site was
high even in early spring. The scale adopted (12 height categories in the first
metre and then each metre thereafter) clearly reduced the categories in arboreal
vegetation; this is, however, still the most diverse. Moreover, it is true that
changes in microclimate that will affect the associated fauna occur over much
smaller height differences in the first metre above ground, than thereafter.
Architectural diversity
The types of plant structure, listed in Table 1, were utilized as the categories.
Architectural complexity also increases through successional stages, although not
as markedly as spatial complexity (Table 3). The Old Field is dominated by
monocotyledons and this may be reflected in its low architectural diversity.
Taxonomic diversity of Heteroptera and Coleoptera
Both these groups contain phytophagous, predatory and fungivorous species,
although no fungivorous Heteroptera were found. In a later study we intend to
investigate diversity patterns in different trophic groups, but here we are
concerned simply with the relationship of insect diversity to plant diversity.
,&diversity
The Indices of Similarity between the insects sampled in the period MayOctober from the different sites show the same trends as those for the vegetation
PLANT AND INSECT DIVERSITIES
337
2
8
f
n
8
g z
U
3
n
cm
3
I
Rank
Rank
Figure 4. Doininance tiiverslty curves for six samples of green plants from sites of different
successional age (age in months in parenthesis). A. ‘Rising’ set with increasing diversity (and
equitability) for [he first 16 months of succession. B. ‘Falling’ set with decreasing diversity from 16
months of succession. 0, Young Field (age 1.5 months); 0 ,Young Field (age 15.5 months); 0 ,Young
Field (age 18.5 months); A, Old Field (age 7 7 months); A, Woodland (age 725 months).
(compare Table 4 with Table 2). Namely, the relative consistency of the insect
fauna in the Woodland and Old Field sites in successive years, and between those
in the Young Fields of up to six months in successional age in successive years,
although these are different sites. However, the similarity between sites of
different successional age (even the Young Field in the same site in successive
years) is low. The indices also show the closer resemblance of the Young Field
after one year to the Old Field than to the New Young Field (Is=O.40, 0.34 cf.
0.26, 0.2 1 for Heteroptera and Coleoptera respectively). It will be noted that the
indices for the insect fauna are lower than those for the plants, we believe this is
largely a reflection of the greater mobility and species richness of the insects. The
Coleoptera, where there are many predatory and saprophagous species show the
trends less clearly and have lower indices than the Heteroptera.
338
T. R. E. SOUTHWOOD E T AL.
Ruderols
Mid wccessionols
Late
successionols
Figure 5 . Spatial diversity profiles for the vegetation. (Note: scale rhange o n vertical axis.)
The species accumulation curves for the insects in the Young Field over two
seasons are shown in Fig. 7 and should be compared with Fig. 1 for the vegetation. The similarities in shape, including the suggestion of a ‘ruderal phase’
are striking.
a - diversity
The a-diversities of the year’s catches of the Coleoptera and Heteroptera of the
three sites do not show any major difkrences (Table 51, but when the dominance
diversity curves for samples are examined (Fig. 8) it is noted that the curves
become shallower (equitability increases) throughout the succession. In the
Woodland site the total number of individuals is high, mainly due to one
abundant species (Kfeidocerys resedue) giving high d values and hence as species
richness is slightly greater, diversity is marginally lower, than in the Old Field
(Appendix 3). When the samples from the Young Field for the first few months of
the succession are considered they have a low species richness, although the small
number of individuals early in the season may give a high diversity index. The
339
PLANT AND INSECT DIVERSITIES
4.c
)
.
3.c
c
$2
%
0
U
2.c
I .c
I
I
I
2
I
I
I
I
I
I
I
I
I
3
4
5
6
7
8
9
10
II
Time( months)
Figure 6. Spatial diversity of vegetation with season. 0, Ruderals; 0 , Early successionals; A, Mid
successionals; A,Woodland.
Table 3. Structural diversity of vegetation
Stage/Site
N
Ruderals, Young Field
Early successionals, Young Field
Mid successionals, Old Field
Late successionals, Woodland
975
1204
2082
1696
Spatial diversity
S
a
SEa
7
12
I1
25
1.0
1.9
1.5
4.2
0.42
0.58
0.49
0.91
Architectural diversity
N
S
a
SEa
2205
4127
2969
4272
14
14
15
20
2.0
1.8
2.1
2.1
0.58
0.52
0.57
0.65
Table 4. Indices of Similarity (Is) between the Heteroptera and Coleoptera
recorded in the different sites between May and October in two seasons
Index
Comparison
~~~
Heteroptera
Coleoptera
0.72
0.65
0.63
0.45
0.40
0.18
0.26
0.55
0.54
0.45
0.34
0.23
0.21
~
Woodland 1977 v Woodland 1978 (same site)
Old Field 1977 v Old Field 1978 (samesite)
Young Field 197 7 v New Young Field 1978 (same age, different site)
Young Field 1977 v Young Field 1978 (different age, same site)
Young Field 1978 v Old Field 1978 (differentageand site)
Young Field 1977 v Old Field 1977 (different a g e a n d site)
New Young Field 1978 v Old Field 1978
0.50
340
T. R. E. SOUTHWOOD E T A L
/ Species in 3 sites
I !
over first season
O-o,
Time (months)
Figure 7. Insect species gain in Young Field over two years. 0, Heteroptera; 0 , Coleoptera.
Table 5 . Total annual diversity (1977) of insects in three sites of different
successional age
~~
~
Site
~~
Heteroptera
N
S
a
Coleoptera
~
Young Field
Old Field
Woodland
137
I18
789
16
19
28
4.7
6.4
5.7
N
SEa
1.39
1.18
1.20
s
~
188
373
285
a
SEa
~~
40
46
45
15.6
13.8
15.0
3.07
2.41
2.71
overall increase in species richness with successional age is shown in Table 6.
Thus the a-diversity of the insects studied rises with successional age of the
habitat throughout the first 16 months and then remains fairly constant (with
seasonal variations), falling only slightly in the Woodland.
Comparison ofplant and insect diversities
The above descriptions suggest that whereas plant and insect (Heteroptera and
Coleoptera) taxonomic diversities rise together with successional age up to about
34 1
PLANT AND INSECT DIVERSITIES
Table 6. Species richness of insects in relation to successional age
1977
Site
Stage
Youiig Field
Ruderal
Early successional
Old b leld
Woodldnrl
Mid auc~essional
Ldte successional
1978
Heteroptera
Coleoptera
Heteroptera
Coleoptera
11
26
12
22
38
61
19
46
18
42
30
50
29
59
Rank
Figure 8 . Dominance diversity curves for insects from sites of different successional age (age in
months in parenthesis).0,Young Field (age 1.5 months);0, Young Field (age 15.5 months);A, Old
Field (age 7 7 months); A, Woodland (age 725 months).
20
342
T. R. E. SOUTHWOOD E T AL.
16 months, the diversity of the insects does not fall to the same extent as that of
the vegetation in later successional stages. This conclusion is supported by a
comparison of the species accumulation curves for the two groups, most easily
made by plotting accumulated insect (Heteroptera and Coleoptera) species
against accumulated green plant species (Fig. 9). In the Young Field the
relationship is virtually linear, the sloped around 4 5 O showing that the rate of
accumulation of insect and plant species (excluding fungi) are comparable
(correlation coefficient r=0.99); there is no asymptote on either axis and this is a
reflection of the actual turn-over in species (shown in Fig. 1) by the plants. In the
Old Field and Woodland sites the plant species has reached a asymptote,
successional change is slower in sites of these ages and so there is very little
species turnover. The relatively greater richness of the species of Heteroptera and
Coleoptera in these sites is shown by the continued accumulation of species, the
differences are particularly striking in regard to the Woodland site.
This relationship is also shown if the mean number of insect species is
compared with the mean number of plant species for each site (Fig. 10A).That is,
plant and insect taxonomic diversity are not associated in the Woodland site in
the way that they are in Young and Old Fields. The diversity of the larger fungi
(Appendix 2) appears to show a similar trend to that of these insect groups.
Plant species gain
Figure 9. Relationship between insect and plant species accumulation in the three sites over two
years. 0, Young Field; A, Old Field; A,Woodland.
PLANT AND INSECT DIVERSITIES
343
-
00
r.093
bigurc 10. Kelatir~nsliipbetween number of insect species and A, mean number of plant species; B,
with tlir addition 01 spatial complexity; C, with the addition of spatial and architectural complexity.
0,
Rudcrals; 0, Early succcssionals; A, Mid successionals; A, Woodland.
I f plant structural complexity provides the additional component to explain
the high diversity of insects in the later successional stages, then the addition of
this to the number of plant species should show a closer correlation for all sites.
Spatial complexity was included by incorporating the number of height
categories recorded for each sampling occasion to the ant species mean (Fig.
10B). Additionally the other component of structuraf ]diversity, architectural
diversity, was incorporated in a similar way to give a composite mean for the
number of plant species and structures (Fig. 1OC).This gave a stronger correlation
with the mean number of insect species for each site ( r = 0.93 cf. r= 0.1 1).
The details of this relationship may be seen against successional age in Fig. 11.
I
Cog N+l Time ( monlhs)
k i K i w 1 1 . I'lw roiiiparative diversities ol~plantsand insects (Heteroptera and Coleoprera) in relation
log w'(cbhiial agr of. thc. habilat. 0,Ruderals; 0, Early succ.&onals; A, Mid sutcrssional~:A,
11)
\.vIll l d l ' ~ l l ~ l .
344
T. R. E. SOUTHWOOD ET AL.
SUMMARY AND CONCLUSION
The taxonomic diversity of the vegetation was seen to rise rapidly in the young
sere, but fell after a successional age of about 16 months. The dominance
diversity curves are similar to those recorded from Old Fields by Bazzaz ( 197.51,
but in the sere he studied, diversity and equitability continued to rise to a greater
successional age. Structural complexity, both in terms of spatial and architectural
components rose throughout succession.
The taxonomic diversity of the Heteroptera and adult Coleoptera rose proportionally with the taxonomic diversity of the plants in the early seral stages, but
in the Woodland stage this fell though not to the same extent as the vegetation.
We conclude that Murdoch et al. (1972)were correct in associating insect diversity
with plant taxonomic diversity in the early seral stages, but in plant communities
that are approaching the climax stage their structural attributes become
increasingly important, as postulated by Lawton (1978).
ACKNOWLEDGEMENTS
We are most grateful to those colleagues who assisted us with some of the
identification of particular groups: Dr P. Hammond (Staphylinidae), Dr C.
Johnson (Ptilliidae: Atomaria, Acrotrichis spp.), M r E. E. Green (larger fungi), Mr
G. McGavin (Mirid nymphs), Dr J. Bates 8c Mr J. Kitchenside (Bryophytes), Drs
N. Bell 8c A. Morton (Gramineae);the bulk of the identifications were made by
ourselves and one of us (TRES) was largely responsible for Heteroptera and
Coleoptera identifications. Several persons kindly assisted us with sampling and
sorting our catches, especially Miss E. Mason, Mrs M. Reese and M r P.
Thompson, whilst Dr D. R. Strong critically reviewed the manuscript.
REFERENCES
BAKER, R. R., 1978. Evolutionary Ecology ofAnimal Migration: 1012 pp. London: Hodder & Stoughton.
BAZZAZ, F. A., 1975. Plant species diversity in old field successional ecosystems in southern Illinois. Ecology, 56:
485-488.
FEENY, P., ‘976. Plant apparency and chemical defense. In J. W. Wallace & M. J . Mansell (Eds), Biochemical
Interaction between Plants and Insects. Recent Advances in Phytochemistry: 10: 1-40.
FINDLEY, J. S . , 1973. Phenetic packing as a measure of faunal diversity. American Naturalist, 107: 580-584.
HARPER,J. L., 1977. PoPulationBiologyofPlants:892pp:London: Academic Press.
HORN, H. F., 197 1. The Adaptive Geometry of Trees: 144 pp. Monographs in Population Biology. New Jersey:
Princeton University Press.
JAMES, F. C., 197 1. Ordinations of habitat relationships among breeding birds. Wilson Bulletin, 83: 215-236.
KARR, J . R., 1968. Habitat and avian density on strip-mined land in east central Illinois. Condor, 70: 348-357.
KARR, J. R. &JAMES, F. C., 1974. Eco-morphological configurations and convergent evolution in species and
coinniunities. In M. L. Cody & J. M. Diamond (Eds), Ecology and Evolution of Communities: 258-288.
Cambridge, Massachusetts & London: Harvard University Press.
LAWTON, J. H.. 1978. Host-plant influences o n insect diversity: the effects of time and space. In L. A. Mound
& N . Walolf (Eds),Diversity oflnsect Faunas. Symposium ofthe Royal Entomological Society ofLondon, 9: 105-125.
MACARTHUR, R. H., 1960. O n the relative abundance of species. American Naturalisf,9 4 : 25-36.
MACARTHUR, R. H. & MACARTHUR, J . W., 1961. O n bird species diversity. Ecology, 42: 594-598.
MAY, R. M., 1976. Patterns in multi-species communities. In R. M. May (Ed.), Theoretical Ecology: 142-162.
Oxford: Blackwells.
MURDOCH, W. W., EVANS, F. C. & PETERSON, C. H., 1972. Diversity and pattern in plants and insects.
Ecology, 53; 819-829.
PIANKA, E. R., 1970. O n r- and K- selection. American Naturalist, 104: 592-597.
RECHER, H. F., 1969. Bird species diversity and habitat diversity in Australia and North America. American
Naturalist, 103: 75-80.
RICKLEFS, R. E., 1973. Ecology, 861 pp. London: Nelson.
PLANT AND INSECT DIVERSITIES
345
SOUTHWOOD, T. R. E., 1977a. Habitat, the templet for ecological strategies?Jounzal ofAGrnd Ecology, 46:
337-365.
SOUTHWOOD, T. R. E., 1977b. The stability of the trophic milieu, its influence o n the evolution of behaviour
and of responsiveness oftrophic signals. Colloques Internationaux du C.N.R.S.,No. 265: 47 1-493.
SOUTHWOOD, T. R. E., 1978. EcologicalMethods, 2nd ed.: 524 pp. London: Chapman & Hall.
STRONG, D. R. & LEVIN, D. A,, 1979. Species richness ofplant parasites and growth form of their hosts. The
American Naturalist, 113 (7).
TANSLEY, A. G., 1939. The BritishIslands and Their Vegetation, I . Cambridge University Press.
TAYLOR, L. R., KEMPTON, R. A. & WOIWOOD, I. P., 1976. Diversity statistics and the log-series model.
Journal of Animal Ecology, 45: 255-272.
VAN VALEN, L., 1965. Morphological variation and width of ecological niche. American Naturalist, 99:
377-390.
Sepr 78
July 7 7
Sepr 7 7
May 78
Ju1> 78
sept i n
90
7 23
725
732
7 34
737
May 78
J U I 78
~
July 7 7
Sept 7 7
76
78
85
88
8
in
17
15
16
14
10
11
I2
9
0.32
0.40
0.20
0.27
0.23 0.36
0.36 0.6
0.27 0.32 0.34 0.5
0.04 0.04
0.04 0.04
< 0.10
0.80 0.94 0.89 0.74
0.05 0.10 0.12 0.06 0.05 0.05 0.05 0.84
0.05 0.09 0.12 0.05 0.05 0.05 0.05
0.31 0.41 0.44 0.70 0.70 0.70
0.37 0.42 0.32 0.66 0.65 0.69 0.74
0.15 0.26 0.44 0.41 0.41 0.73 0.70 0.77 0.75 0.71
0.04
0.04
0.07
0.11
0.11 0.06 0.04
0.10 0.06 0.04
0.09
0.11
0.10
0.09
0.10
0.84
w
m
J1
No. m4
27 0
27.0
27.0
Fungal fruiting bodies
7
Oct. 1977
79
Oct. 1977
7 20
Oct. 1977
721
722
7 23
124
7 26
732
7 33
734
135
736
7 20
89
88
85
86
87
81
225
225
225
225
225
225
225
225
450
450
225
225
225
270
225
225
225
225
225
180
180
90
180
180
180
180
180
180
450
225
225
225
225
225
225
=Apr.
May 1977
MayfJun.
Jun./Jul.
Jul./Aug.
Aug.
Sep .
Jan. 1978
May
Jun.
Jul.
Aug.
Sep .
May 1977
MayfJun.
Jun./Jul.
late Jul.
Aug.
Sep .
Jan. 1978
Apr./May
Jun.
Jul.
Aug./Sep.
Sep./Oct.
May 1977
Ma y/J un .
Jun./Jul.
Jul./Aug.
Aug.
Sep.
May 1978
Jun.
Jul.
Aug.
Sep.
Seed bank
1.5
2.25
3.25
4.5
5.25
6.25
9.75
13.75
14.75
15.75
17.25
18.25
73
74
75
76
77
78
No.
sampling
point
Sampling
date
Successional
age
months
5.0
8.9
8.1
262
56 7
430
662
741
373
449
582
52 7
695
62 7
359
410
43 7
455
50 7
468
33 I
394
465
416
453
380
6
11
13
27
23
37
48
133
124
394
182
393
349
364
376
495
4 10
49 1
42 1
8
2
2
9
8
10
10
8
9
11
11
8
8
8
32
46
45
41
42
31
34
28
34
25
26
28
31
32
34
30
33
32
37
S
N
0.4
1.2
2.1
1.4
1.6
1.8
7.9
7.9
6.9
7.2
7.1
2.1
2.1
1.4
1.4
1.3
1.6
1.5
1.9
8.0
2.8
3.7
6.6
7.0
10.0
10.5
8.5
13.8
12.0
13.7
11.0
7.7
9.0
7.9
7.9
5.8
5.4
5.8
1.8
a
0.88
0.29
1.23
1.76
1.55
1.32
1.19
1.22
1.67
1.60
1.54
1.43
1.42
1.42
0.72
0.70
0.54
0.54
0.52
0.58
0.58
0.65
0.63
0.55
0.58
1.80
1.97
1.59
2.36
0.88
0.99
1.19
1.45
1.73
1.92
2.02
1.73
2.40
2.09
SEA
0.88
0.80
0.47
0.28
0.28
0.25
0.22
0.51
0.44
0.42
0.39
0.35
0.38
0.54
0.46
0.41
0.43
0.41
0.33
0.23
0.33
0.28
0.31
0.38
0.38
0.30
0.43
0.15
0.50
0.44
0.28
0.40
0.27
0.18
0.49
0.35
0.32
0.20
d
17
24
28
33
334
389
225
225
Aug./Sep.
Sep./Oct.
10
S
56
224
431
N
450
225
225
No.
Apr./May
Jun.
Jul.
Sampling
date
Basic taxonomic diversity and indicesfor t h vegetation ofthe three sites
APPENDIX 2
1.59
1.74
7.3
8.6
1.37
1.19
1.27
SFa
3.5
4.3
5.5
a
0.19
0.17
0.33
0.16
0.20
d
1
U
z
>
-I
Fz
-a
10.0
13.5
14.5
15.5
18.5
73
74
76
78
81
85
86
87
89
720
721
722
7 24
728
732
733
734
736
6.0
1.5
2.0
4.0
Successional
age
Months
Sep.
Jan. 1978
May
Jun.
Jul.
Sep.
JuI.
May 1977
May/J un.
Jul.
Sep .
Jan. 1978
May
Jun.
Jul.
Sep.
May 1977
May/Jun.
Jul.
Sep.
Jan. 1978
May
Jun.
Jul.
Sep.
May 1977
May/Jun.
Sampling
date
127
114
42
213
90
96
68
109
129
50
86
23
173
177
210
215
420
54
230
205
172
327
10
20
19
152
124
N
10
11
29
27
8
41
28
14
38
29
28
26
31
I8
24
17
7
26
30
32
46
36
9
33
27
35
35
S
8.0
10.9
10.6
10.6
18.6
21.0
11.9
7.4
13.5
14.8
13.3
15.4
14.5
5.7
18.1
6.4
3.4
8.5
10.4
10.5
17.9
9.4
3.1
10.6
8.3
13.3
9.9
a
3.84
5.40
2.44
2.56
15.16
4.38
2.85
2.64
2.67
3.68
3.29
4.19
3.38
1.61
5.54
1.91
1.71
2.01
2.31
2.24
3.31
1.82
1.25
2.21
1.91
2.79
1.97
SEA
0.20
0.26
0.18
0.26
0.58
0.24
0.44
0.43
0.47
0.15
0.09
0.22
0.54
0.70
0.24
0.49
0.23
0.68
0.32
0.30
0.21
0.24
0.44
0.20
0.39
0.24
0.26
d
May 1978
May/Jun.
Jul.
Sep.
Sampling
date
71
97
68
236
N
18
26
24
31
S
7.8
11.6
13.2
9.5
a
2.34
2.95
3.68
2.04
SEa
Basic taxonomic diversity data and indicesf o r the insects (Heteroptera and Coleoptera) ofthe three sites
APPENDIX 3
~
0.21
0.37
0.12
0.42
d
I’
b
m
gr
co